![]() “I think it brings an interesting piece of evidence to this question,” said Humphrey. Together, all this water loss explained the eastward change in polar drift. ![]() They found that the contributions of water loss from the polar regions is the main driver of polar drift, with contributions from water loss in nonpolar regions. Using data on glacier loss and estimations of ground water pumping, Liu and her colleagues calculated how the water stored on land changed. “The goal of this project, funded by the Ministry of Science and Technology of China is to explore the relationship between the water and polar motion.” Water loss and polar drift “The findings offer a clue for studying past climate-driven polar motion,” said Suxia Liu, a hydrologist at the Institute of Geographic Sciences and Natural Resources Research at the Chinese Academy of Sciences, the University of the Chinese Academy of Sciences and the corresponding author of the new study. The new research calculates the total land water loss in the 1990s before the GRACE mission started. Now researchers have found a way to wind modern pole tracking analysis backward in time to learn why this drift occurred. The average speed of drift from 1995 to 2020 also increased about 17 times from the average speed recorded from 1981 to 1995. In 1995, the direction of polar drift shifted from southward to eastward. In particular, they wanted to see if it could also explain changes that occurred in the mid-1990s. The authors of the new study believed that this water loss on land contributed to the shifts in the polar drift in the past two decades by changing the way mass is distributed around the world. Other shifts were caused in part by what’s called the terrestrial water storage change, the process by which all the water on land - including frozen water in glaciers and groundwater stored under our continents - is being lost through melting and groundwater pumping. For example, research has determined more recent movements of the North Pole away from Canada and toward Russia to be caused by factors like molten iron in the Earth’s outer core. Previous studies released on the GRACE mission data revealed some of the reasons for later changes in direction. The mission gathered information on how mass is distributed around the planet by measuring uneven changes in gravity at different points. Researchers have been able to determine the causes of polar drifts starting from 2002 based on data from the Gravity Recovery and Climate Experiment (GRACE), a joint mission by NASA and the German Aerospace Center, launched with twin satellites that year and a follow up mission in 2018. The same thing happens to the Earth as weight is shifted from one area to the other. If the weight of a top is moved around, the spinning top would start to lean and wobble as its rotational axis changes. The Earth spins around an axis kind of like a top, explains Vincent Humphrey, a climate scientist at the University of Zurich who was not involved in this research. “The faster ice melting under global warming was the most likely cause of the directional change of the polar drift in the 1990s,” said Shanshan Deng, a researcher at the Institute of Geographic Sciences and Natural Resources Research at the Chinese Academy of Sciences, the University of the Chinese Academy of Sciences and an author of the new study. Melting glaciers redistributed enough water to cause the direction of polar wander to turn and accelerate eastward during the mid-1990s, according to a new study in Geophysical Research Letters, AGU’s journal for high-impact, short-format reports with immediate implications spanning all Earth and space sciences.
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